The present invention relates to a process for the hydroformylation of olefins to produce aldehydes and alcohols. The present invention more particularly relates to such a process in which anionic transition metal complex catalysts are used which are extremely selective toward straight chain products. The present invention more particularly relates to the use of mixed metal complexes as hydroformylation catalysts.
Aldehydes and alcohols are extremely useful as general purpose solvents, as surfactants and as precursors to many other useful chemicals. Due to the extent to which these compounds are used, it is important that such compounds be biodegradable. One important factor effecting the biodegradability of aldehydes and alcohols is the linearity of the molecule. Linear aldehydes and alcohols are more easily biodegraded than branch-chain aldehydes and alcohols. In addition, certain straight chain aldehydes and alcohols are extremely useful in particular applications.
One particular straight chain aldehyde which has particular utility is n-butyraldehyde. This aldehyde can be dehydrated to form 2-ethyl hexanol which is useful as a gasoline additive or the aldehyde can be esterified with phthalic anhydride to produce dioctylphthalate which is used for plasticizing polyvinyl chloride resins.
The straight chain alcohols or esters of the straight chain alcohols are useful as surfactants or soaps which are biodegradable. Particularly useful are C.sub.12 to C.sub.18 alcohols and the esters of these alcohols.
One method of producing aldehydes and alcohols is the hydroformylation of olefins. Hydroformylation is an old reaction and is used commercially to prepare both straight and branch-chain aldehydes and alcohols. In this reaction, an olefin is reduced by the addition of carbon monoxide and hydrogen to form an aldehyde. This reaction can be carried further until the aldehyde is reduced to an alcohol. This is further explained in U.S. Pat. No. 3,876,672 which is incorporated herein by reference.
The hydroformylation reaction generally requires a catalyst. In the past, typical catalysts have included cobalt carbonyl, rhodium carbonyl, nickel, and platinum complexes, as well as monovalent ruthenium cluster complexes. A problem encountered with most of these prior art catalysts was the poor selectivity toward linear aldehydes or alcohols.
Therefore, it is an object of the present invention to disclose a process for the hydroformylation of olefins to produce a high percentage of linear aldehydes or alcohols and low percentage of branch-chain aldehydes or alcohols.